The present invention relates to a control fixture for a tire bead compression testing machine.
In the manufacture of tires, xe2x80x9cbead contact pressurexe2x80x9d (i.e., the pressure at which the tire is carried on the wheel rim) is an important parameter. This pressure must be high enough to overcome the forces encountered when the vehicle is traveling at high speeds or negotiating a turn, but not so high as to prevent removal of the tire from the rim. Accordingly, quantifying bead compression characteristics is often an important part of tire testing procedures.
A conventional apparatus for determining bead compression characteristics comprises a plurality of clamp segments (e.g., eight) distributed around the circumference of a circle and mounted for selective radial movement. The clamp segments are shaped to collectively form a clamping jaw which approximates the geometry of a wheel rim. Force-sensing instrumentation (e.g., a load cell) is attached to at least some of the clamp segments. A tire is placed in a horizontal orientation on the apparatus with the to-be-checked bead positioned downwardly. The clamp segments are then moved radially outward (preferably simultaneously and for the same distances) and resistance of the tire against this movement is measured by the force-sensing instrumentation. In this manner, bead compression characteristics can be quantified for the tire.
The present invention provides a control fixture for checking a bead compression testing apparatus to ensure test-to-test consistency.
More particularly, the present invention provides a control fixture comprising a plurality of plunger assemblies. Each plunger assembly includes a plunger, a casing for sliding receipt of the plunger, and a spring positioned between the plunger and the casing. To confirm the consistency of the tire-bead compression testing apparatus, each plunger is attached to a respective one of the radially movable segments. The segments are moved outward, and the spring constant of each of the springs is measured with the force-sensing instrumentation.
The present invention provides these and other features hereinafter fully described and particularly pointed out in the claims. The following description and drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention can be employed.